U.S. Pat. No. 3,920,753 discloses that glycol aldehyde, which is a useful intermediate for the preparation of ethylene glycol, which is itself an extremely valuable commercial chemical, can be prepared by the reaction of formaldehyde with carbon monoxide and hydrogen in the presence of a cobalt catalyst. U.S. Pat. No. 4,200,765 and European Patent Application No. 2908, both disclose that this same chemical reaction can be carried out using a rhodium catalyst instead of a cobalt catalyst.
These prior art processes suffer from the disadvantage that much methanol is produced as a result of the hydrogenation of formaldehyde which proceeds as a side-reaction. In order to suppress the methanol production to a reasonable level, the prior art processes use very high pressures; in addition, they use carbon monoxide/hydrogen gas mixtures with a relatively high carbon monoxide content.
It has now been found that the production of glycol aldehyde in this type of process, when using either a cobalt or a rhodium catalyst, can be improved by the addition to the reaction mixture of a catalytic amount of a strong protonic acid. In particular, the quantity of methanol formed can be much reduced.